Method of and an apparatus for the heat treating of metal pipe



July 4, 1967} A T SCHMIDT 3,328,988

METHOD OF AND AN APPARATUS FOR THE HEAT TREATING OF METAL PIPE Filed Feb. 16, 1965 Sheets-Sheet 1 Theodor SchmicH' 1N VENTOR.

BY I 5 Attorney July 4, 1967 T SCHMIDT 3,323,988,

METHOD OF AND AN APPARATUS FOR THE HEAT TREATING OF METAL PIPE I g Sheets-Sheet 2 Filed Feb. 16, 1965 Fig.3

Attorney United States Patent 3,328,988 METHOD OF AND AN APPARATUS FOR THE HEAT TREATING 0F METAL PIPE Theodor Schmidt, Essen, Germany, assignor to Indugas, Gesellschaft fiir Industrielle Gasverwertung m.b.H., Essen, Germany, a corporation of Germany Filed Feb. 16, 1965, Ser. No. 433,144 Claims priority, application Germany, Feb. 18, 1964, J 25,305 15 Claims. (Cl. 72-128) My present invention relates to a method of and an apparatus for the heat treatment of metal pipe and similar elongated stock.

The heat treatment of elongated metallic bodies has been carried out earlier in a variety of ways with many different devices; thus, for example, it has been common practice heretofore to provide elongated muffle-type furnaces, gas-heated elongated ovens, electric-heating chambers and the like which generally extend linearly along the pipe over the length thereof or at least a substantial part of this length. When it is desired to heat treat seamless tubes or pipe or tube blooms, longitudinally extending furnaces or heating muflles have been provided, with lengths on the order of hundreds of meters, to bring the pipe to the desired deformation temperature (i.e. a temperature at which the metal is plastically deformable but the pipe does not collapse) whereupon the heated pipe or bloom can be stretched. With iron pipe and the like, the temperatures to which these elongated furnaces arise the pipe are in the region of 950 C. It is also frequently advantageous to heat treat welded pipe or the like to reform the crystal structure of the metal pipe in the region of the weld and, for this purpose, the pipe can be subjected to an annealing heat treament at the recrystallization or normalization temperature in accordance with conventional methods. While many furnace structures, pipe-support arrangements and heating devices have been proposed for these purposes, the major technological problems reside in the considerable length required for such furnaces. It is the principal object of the present invention, therefore, to provide a method of and an apparatus for the heat treatment of metal pipe and especially iron pipe whereby this disadvantage can be obviated.

It is a more specific object of this invention to provide a method of and an apparatus for the heat treatment, with or without reduction in cross-section, of metal pipe which enables the furnace arrangement to be more compact than possible heretofore and yet affords results obtainable only with heating units of considerable lengths.

These objects and others which will become apparent hereinafter are attainable, in accordance with the present invention, as a result of my discovery that, contrary to what may have been expected, a metal pipe can be continuously deformed through an are (preferably extending over at least 180 about a substantially vertical axis) and then passed into a heating device along this are for the usual heat treatment, the pipe thereafter being straightened, preferably in its heated state. Upon conclusion of the latter operation it is found that straightening of the pipe does not produce any reduction of essential physical properties, as compared with pipe maintained in a linear condition throughout its heat treatment. For metal pipe, and especially for iron pipe, it has been found that the are along with the pipe is bent should not have a radius of curvature less than substantially meters if collapse of the pipe and permanent distortion, remaining after straightening, is to be avoided, and that for overall compactness of the operation, the maximum radius of curvature should not significantly exceed 20 meters. When, according to this invention, as described in greater detail below, the arc extends through a full circle, this circle can have a radius ranging between substantially l0 and 20 meters or a diameter between substantially 20 and 40 meters.

According to the method aspect of the invention, the heating of the arcuately bent pipe is carried out substantially continuously and, advantageously, to a temperature sufficient to render the pipe plastic'ally deformable but less than that at which the pipe tends to collapse, this temperature being approximately 950 C. when iron pipe is employed and is to be stretched. I have found that the stretching operation can take place subsequent to the straightening of the heated pipe but more advantageously is carried out concurrently with or prior to such straightening as the pipe is continuously displaced along the arc.

The apparatus for practicing the instant invention thus will comprise a bending means for continuously bending the metal pipe through the arc of at least 180 about a generally vertical axis, a heating means forwardly of this bending means for raising the temperature of the pipe to the indicated level, straightening means forwardly of the heating means for continuously straightening the arcuately bent and heated pipe, and means for continuously feeding the pipe through the bending, heating and straightening means in succession. The heating means can include an arcuate elongated heating chamber extending continuously over a substantial fraction of the arc in excess of 180 through which the pipe is bent or, as is preferred, a plurality of angularly spaced heating chambers or mufiles disposed about the arc and receiving the pipe as it passes between the bending means and the straightening means. These heating sections can then be disposed along the sides of a polygon and need not have an arcuate configuration if the width of the respective furnace chambers is sufficient to accommodate the included arc segments of the bent pipe. Between these heating sections, a guide means, preferably constituted by pairs of rollers having vertical axes, can be disposed for supporting the pipe.

According to another feature of the present invention, guide means is also provided for diverting the pipe helically through the heating means in at least two passes, although any desired number of turns can be used; the guide means can then include vertically spaced pairs of rollers as well. After one or more turns along this helical path, the pipe is led out of the apparatus through the straightening means, as indicated earlier.

Still another feature of the present invention resides in the construction of the bending and/or straightening means, either or both of which can comprise a pair of rollers displaceable about respective vertical axes and spaced along the pipe while in engagement with one side thereof, and a further roller engaging the other side of the pipe so that the three rollers can distort the pipe into the arc or reform it into a linearly extending body. It should be noted that the sectoral furnace described above can be continued around the remainder of the helix and thus have a complete annular configuration, with the bending means and the straightening means being so disposed as to lead the pipe tangentially into and from the annular furnace chamber. While the heating unit or units may be provided with a plurality of vertically spaced chambers to accommodate the various turns of the helically bent pipe, it has been found that excellent results are obtained when a single chamber accommodates a plurality of turns, as will be apparent hereinafter. When the term mufile is used herein with reference to the heating units, it must be understood to include any furnace enclosure through which the pipe can pass; this enclosure being provided with the usual heating devices. The guide, bending and straightening rollers can be driven with identical peripheral speeds in the event no permanent deformation of the pipe is required or with increased speed from the inlet to the outlet side of the apparatus whereby these rollers and the drive means therefor can constitute a straightening means adapted to elongate the pipe and reduce its cross-section, if desired. Additional rollers with horizontal axes can be provided forwardly of the bending means or elsewhere along the arc to assist in supporting the pipe.

The above and other objects, features and advantages of the present invention will be more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. 1 is a diagrammatic plan view of a heat treating installation for metal pipe according to this invention;

FIG. 2 is a cross-sectional view taken generally along the line IIII of FIG. 1;

FIG. 3 is a view taken along the line III-III of FIG. 1;

FIG. 4 is a diagrammatic plan view showing a two-turn furnace arrangement;

FIG. 5 is a cross-sectional view taken along the line VV of FIG. 4;

FIG. 6 is a view similar to FIG. 5 showing a three-turn arrangement.

In FIG. 1, I show a plant for the heat treating of metal pipe P which is advanced in the direction of arrow 10 along a plurality of rollers 2 journaled upon substantially horizontal axes to a supporting means, not illustrated. At the inlet side of the plant, a bending means generally designated 1 is provided for deforming the pipe into an arc of at least 180 with a radius of curvature of substantially 10 to 20 meters. Along this arc, a plurality of angularly spaced heating mufiles 3a3d is provided along the sides of a polygon, the chamber 3' (FIG. 2) of each mufile 3a-3d having a width sufficient to permit reduction or increase of the radius of curvature of the arc and the bending of the pipe within each longitudinally extending muffle without contact with the interior walls thereof. Each mufile can be provided with a duct 11 from which combustion or heating gases can be removed and a plurality of burner nozzles 12 through which a burning mixture of fuel and air can be introduced, this mixture having a stoichiometric excess of fuel so as to provide a reducing atmosphere in the interior of the muflle. When the pipe is bent through at least a full circle (dot-dash line P) according to the invention, additional heating sections can be provided. It is also possible, as indicated earlier, to provide an interrupted and sectoral heating unit 3e over a substantial portion of the arc of 180 or even over the entire arc. For a half-turn system, as illustrated in solid lines in FIG. 1, a straightening means generally designated 4 is provided forwardly of the last heating unit 3d. Pairs of rollers 5a, 5b engageable with the pipe P from opposite sides and journaled about respective vertical axes, serve as the guide means between the heating units for supporting the pipe. When two or more turns are used, each of the pairs of axes can accommodate vertically spaced pairs of rollers respectively engageable with the several turns.

The bending means, according to the persent invention, can include a plurality of rollers at least two of which (i.e. rollers 13 and 14) are provided on one side of the pipe P while a further roller 15 is disposed upon the other side and is urged by suitable spring or hydraulic compression means against the pipe to bend it through the arc. As illustrated in FIG. 3, for example, the rollers 14 and 15 can be disposed in contoured pairs 14', 15 threadedly displaceable toward and away from one another u-pon the respective spindles 14", 15" while being provided with suitable locking units to accommodate the rollers to pipe of substantially any outer diameter. The roller pairs of 5a and 5b are similarly adjustable. The spindles 14" and 15" are journaled in the fixed support 14a and the transversely movable support 15a, respective- :ly, the latter co-operating with a hydraulic means 15b adapted to shift the roller 15 toward the common axial plane of rollers 13 and 14 and adjust the radius of curvature of the arc. The movable support 15a also carries a servomotor 15c coupled with the spindle 15 for displacing the pipe P at the bending means. The servomotor 15c can be coupled by the usual transmission means with one or more of the roller pairs 5a and 5b with a suitable reduction so that the successive rollers 5a, 512 have higher peripheral speeds than the peripheral speed of roller 15 and the pipe is elongated and is reduced in cross-section as it passes through the heating unit. The straightening device 4 can be constructed similarly, rollers 113 and 114 being fixedly disposed upon one side of the pipe and a transversely displaceable roller 115 on the other. The servomotor of the straightening arrangement is then coupled with that of the bending means to further elongate or stretch the pipe. The se'rvocontrol device 16 can include one or more sensing devices 17 responsive to the diameter of the pipe P for actuating the pressure means 15b or changing the relationship between the peripheral speeds of the several rollers and thus vary the diameter of the arc or augment or reduce the stretching in accordance with the desired pipe diameter. The roller pairs 5a and 5b and the muflles 3a-3d can be shiftable with respect to the radius of the arc toward and away from the latter to permit different arc radii to be employed. For this purpose, radial rails diagrammatically shown at 17' can be used while the rollers 5a and 5b are mounted on a comsupport similar to that shown at 15a.

In 'FIG. 4, I show an arrangement wherein the heating rnufiles 103a-103c etc. and the roller pairs 105 are disposed about a complete circle and each roller pair 105 accommodates two vertically spaced roller portions engaging the pipe at the pitch h of the helix. Thus, the pipe passes twice through the vertically elongated heating chamber 103' of each heating muffle after bending at 101 and prior to straightening at 104. A three-pass system is illustrated in the muffle 203 of FIG. 6, as previously noted, the muflies are preferably designed to bring the pipe to a temperature sufficient to effect plastic deformation of the pipe but insufiicient to cause its collapse. For this purpose, a temperature of about 950 C. is particularly desirable for iron pipe.

I claim:

1. A method of heat treating metal pipe, comprising the steps of continuously bending said pipe through an arc of at least 180; heating the arcuately bent pipe substantially continuously to a temperature sufiicient to render it plastically deformable but less than that at which said pipe will collapse; and continuously straightening the arcuately bent and heated pipe.

2. A method of heat treating metal pipe, comprising the steps of continuously bending said pipe through an arc of at least 180; heating the arcuately bent pipe substantially continuously to a temperature suflicient to render it plastically deformable but less than that at which said pipe will collapse; continuously stretching the arcuately bent and heated pipe; and continuously straightening the arcuately bent and heated pipe.

3. A method of heat treating iron pipe, comprising the steps of continuously bending said pipe through an arc of at least 180; heating the arcuately bent pipe substantially continuously to a temperature of approximately 950 C. and sufficient to render it plastically deformable but less then that at which said pipe will collapse; continuously stretching the arcuately bent and heated pipe; and continuously straightening the arcuately bent and heated pipe.

4. A method of heat treating iron pipe, comprising the steps of continuously bending said pipe through an arc of at least 180 with a radius of substantially 10 to 20 meters; heating the arcuately bent pipe substantially continuously to a temperature of approximately 950 C. and sufiicient to render it plastically deformable but less than that at which said pipe will collapse; continuously stretching the arcuately bent and heated pipe; and continuously straightening the arcuately bent and heated pipe.

5. An apparatus for heat treating metal pipe, comprising bending means for bending said pipe through an are about a generally vertical axis; heating means forwardly of said bending means for heating said pipe along said are; straightening means forwardly of said heating means for straightening the heated pipe; and means for continuously feeding said pipe in succession through said bending means, said heating means and said straightening means.

6. An apparatus for heat treating metal pipe, comprising bending means for bending said pipe through an arc of at least 180 about a generally vertical axis with a radius of substantially to 20 meters; heating means forwardly of said bending means for heating said pipe along said arc; straightening means forwardly of said heating means for straightening the heated pipe; and means for continuously feeding said pipe in succession through said bending means, said heating means and said straightening means.

7. An apparatus as defined in claim 6 wherein said bending means includes at least two bend-ing rollers disposed on one side of said pipe and a further bending roller disposed on the other side of said pipe intermediate said two rollers, said rollers being in engagement with said pipe and journaled about respective substantially vertical axes.

8. An apparatus as defined in claim 7 wherein said straightening means includes at least two straightening rollers disposed on one side of said pipe and a further straightening roller disposed on the other side of said pipe intermediate said two straightening rollers, said straightening rollers being in engagement with said pipe and journaled about respective substantially vertical axes.

9. An apparatus as defined in claim 8, further comprising means for vertically adjusting each of said rollers for accommodating pipe of different diameters.

10. An apparatus as defined in claim 8, further comprising means for stretching said pipe along said arc prior to the passage thereof through said straightening means.

11. An apparatus as defined in claim 10 wherein said stretching means includes a pair of rollers engaging said pipe along said arc and operable with a peripheral speed in excess of that of said bending rollers.

12. An apparatus as defined in claim 8 wherein said heating means includes a muffle surrounding said pipe over at least a major fraction of said arc.

13. An apparatus as defined in claim 8 wherein said heating means includes a plurality of angularly spaced heating mufiles surrounding said pipe at spaced locations about said are and disposed substantially along the sides of a polygon.

14. An apparatus as defined in claim 13 further comprising guide means intermediate said heating muflles for supporting said pipe along said arc.

15. An apparatus as defined in claim 8, further comprising guide means for directing said pipe helically through said heating means in at least two passes.

References Cited UNITED STATES PATENTS 996,802 7/1911 Schneider 72l34 3,161,225 12/1964 Ward et al 72128 FOREIGN PATENTS 1,037,456 7/ 1966 England.

CHARLES W. LANHAM, Primary Examiner. L. A. LARSON, Assistant Examiner. 

3. A METHOD OF HEAT TREATING IRON PIPE, COMPRISING THE STEPS OF CONTINUOUSLY BENDING SAID PIPE THROUGH AN ARC OF AT LEAST 180*; HEATING THE ARCUATELY BENT PIPE SUBSTANTIALLY CONTINUOUSLY TO A TEMPERATURE OF APPROXIMATELY 950*C. AND SUFFICIENT TO RENDER IT PLASTICALLY DEFORMABLE BUT LESS THEN THAT AT WHICH SAID PIPE WILL COLLAPSE; CONTINUOUSLY STRETCHING THE ARCUATELY BENT AND HEATED PIPE; AND CONTINUOUSLY STRAIGHTENING THE ARCUATELY BENT AND HEATED PIPE. 